The Kolibri!

Unlockable once you reach rank 10 in the Scout class, this is quite possibly the best implemented joke gun I have ever seen in a video game. The animations are pure gold. Seeing as it’s not particularly useful (the bullets might break skin if fired with the wind), some may think the coding that went into it was wasted effort. I say nay. I equip this little beast because pulling it out never fails to make me smile (giggity) which is a stat every bit as important as TTK.